Our previous work indicates that protein phosphatase activity is increased in hippocampus of aged rats and contributes to age-related alterations in synaptic strength and cognition. The proposed studies investigate whether the protein phosphatase calcineurin interacts significantly with several other brain aging biomarkers, including increased Ca2+ channel function and altered gene expression. In each aim of this project, calcineurin activity in hippocampal cultures and in hippocampus of intact rats, is manipulated using recombinant viruses (adeno- and lentivirus). The first specific aim tests whether constitutively active calcineurin causes aging-like changes in voltage sensitive Ca2+ channels (VSCC) (i.e. an increase in L-type VSCC currents and a decrease in N-type VSCC mRNA levels). Molecular interactions of calcineurin with VSCCs also will be explored. The second aim tests whether increased calcineurin activity leads to aging-like changes in global gene expression, as assessed using gene microarrays. The specific role of the calcineurin/NF-AT transcriptional pathway will be explored using recombinant virus containing a potent NFAT inhibitor, VIVIT. The third aim uses recombinant viruses to test whether the calcineurin/NF-AT pathway contributes to age-related memory deficits on the Morris swim task. After completion of behavioral training, intact and partially dissociated hippocampal slices will be prepared from these rats to determine whether the calcineurin/NF-AT pathway also is responsible, in part, for age-related alterations in synaptic strength, plasticity (i.e. long-term potentiation and long-term depression), and L-type VSCC activity. Furthermore, individual neurons and glia will be harvested from zipper slices to examine single cell gene expression profiles using gene microarray technology.